An intervertebral disc located between two vertebrae in the spine provides structural support and distributes forces exerted on the spinal column. Besides holding the vertebrae together, enabling upright posture and natural curvature of the spine (lordosis or kyphosis, for example, within normal physiological ranges), a healthy intervertebral disc enables flexion, extension, lateral bending, and axial rotation of the vertebrae.
The major components of an intervertebral disc include the annulus fibrosus, the nucleus pulposus, and cartilage endplates. The annulus fibrosus is a tough, fibrous ring attached to the vertebrae directly above and below the disc space. The tire-like annulus fibrosus supports the adjacent vertebrae and limits their relative displacements in translation and rotation. The annulus fibrosus also contains the nucleus pulposus. The nucleus pulposus is the central portion of the disc, comprising a relatively soft, gel-like substance that provides many of the articulation and cushioning properties of the intervertebral disc.
Intervertebral discs may be injured or become damaged by disease or aging. A common problem is disc herniation, in which portions of the nucleus pulposus is extruded through an opening in the annulus. Portions of the nucleus pulposus protruding into the vertebral canal may press on a spinal nerve, often resulting in nerve damage, intense pain, numbness, reduced mobility, and muscle weakness. When degeneration or disease of the natural intervertebral disc has progressed to the point where non-operative care such as medication, injections, and/or physical therapy is ineffective, surgical intervention may be required.
A common procedure for treatment of a degenerated or diseased intervertebral disc involves removal of the natural tissues of the disc and fusion of the adjacent vertebrae (intervertebral arthrodesis). Another frequently used procedure, generally considered before the intervertebral arthrodesis, implies the withdrawal of the natural tissues and the replacement of the intervertebral disc by an intervertebral disc prosthesis.